Meeting Abstract
15.6 Monday, Jan. 4 Effects of Food Deprivation on the Insulin-like Growth Factor-I System in Eastern Fence Lizards (Sceloporus undulatus) DUNCAN, C.A.*; COHICK, W.S.; JOHN-ALDER, H.B.; Rutgers Univ., New Brunswick caduncan@eden.rutgers.edu
Based on numerous studies involving food deprivation, previous investigators have concluded that nutritional status is a principal environmental regulator of IGF-I. However, discrepancies exist in the literature regarding severity of nutritional manipulation and correlations between nutritional status, hepatic IGF-I message and plasma IGF-I. For example, in hatchling S. undulatus, food deprivation decreased hepatic IGF-I by 5-fold, while re-feeding restored hepatic IGF-I to the level of the ad libitum fed group. In yearling S. jarrovii, 1/3 ration had no effect on hepatic IGF-I compared to the ad libitum fed group. These data demonstrate that hepatic IGF-I is permissive across a range of food intake and is not continuously scaled to food intake. Thus, the natural significance of nutritional regulation of IGF-I is not well understood, and ecologically realistic levels of nutritional manipulation may not support the conclusion that food is a key environmental regulator of IGF-I. Alternatively, hepatic IGF-I may not serve as a reliable indicator of plasma IGF-I. To test the relationship between hepatic IGF-I and plasma IGF-I, we altered food rations in adult males of S. undulatus. Dietary treatment groups were as follows: Fed (F; 6 crickets/d x 15 d), Unfed (U; 0 crickets/d x 11 d), and Re-fed (R; unfed x 11 d and fed x 4 d). During the 15-d treatment period, F consumed 1.8 crickets/d, and during the 4-d re-feeding period, R consumed 3.2 crickets/d. Body condition worsened and expression of hepatic IGF-I was inhibited by 3-fold in U, while re-feeding for four days restored these effects relative to F. Altogether, results from nutritional manipulation in Sceloporus lizards are consistent with previous work but suggest that food restriction short of starvation may have little effect on the production of IGF-I. Supported by SICB, Graduate School-New Brunswick and School of Environmental and Biological Sciences.
